Soft landings for tough times: the impact of ground cover traits on the overwintering survival of Anisota stigma (Notodontidae) and Manduca sexta (Sphingidae) in urban ecosystems.
Description
Subsurface pupation among arboreal Lepidoptera is widespread and species are vulnerable to microhabitat conditions during this life stage. We investigated how ground cover type influences soil health, subsurface temperature, and fitness in Manduca sexta (Sphingidae) and Anisota stigma (Saturniidae). Overwintering survival decreased in the field compared to controls in growth chambers, with M. sexta experiencing particularly high mortality. Canopy density had a positive relationship with survival in A. stigma. Substrate type also significantly influenced emergence rates, with A. stigma showing the highest success, 36.84%, in forest cover, followed by mulch (29.63%), mature turf (27.50%), layered urban understories (9.80%), recently established turf (5.88%), and bare soil (5.40%). Female overwinter water retention in A. stigma was positively correlated with average daily maximum soil temperature, suggesting the use of discontinuous gas exchange for water conservation under stress. Finally, observed surface-related pupal deaths accounted for a minimum of 16.19% and 8.72% of total overwintering mortality in A. stigma and M. sexta, respectively. Soil compaction, which was negatively correlated with organic matter, and the proportion of bare soil cover was positively correlated with surface pupation in our focal species. The findings reveal that current landscaping practices likely contribute to urban declines in lepidopteran diversity and abundance. These results emphasize the importance of “soft landings” beneath moth host plants, which protect the soil with foliage cover. We recommend soil remediation strategies especially following disturbance, such as mulching or incorporating organic soil amendments, to enhance habitat productivity. Within these pupation sanctuaries, managers should also minimize foot and mower traffic to reduce soil compaction and lower risk of injury to pupae. These data include: Adult moth emergence information, environmental and caterpillar variables for each site, pupae observed on the surface during the fall and winter that did not successfully burrow into soil, and temperature data from subsurface data loggers.
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Institutions
- University of Delaware